1. Field of the Invention
The present invention generally relates to discrimination of low power RF signals and, more particularly, discrimination of low power RF signals utilizing injection locked lasers.
2. Description of the Related Art
The ability to discriminate specific very low power RF signals in a cluttered environment is important in both military and civilian applications such as radio astronomy and channelization. For these applications, it is important to not only determine the frequency of the signal but also not add any loss to the signal. Photonic techniques are preferred for performing these applications as they have broad instantaneous bandwidths. While demonstrations have been proposed to detect RF frequencies in a noisy environment using dispersion, narrow-band optical filters or power monitoring of two lasers, these methods have not focused on preventing loss to very low power RF signals.
Other methods that can be used to detect and amplify low RF power signals include the use of a multi-mode optoelectronic oscillator (MM-OEO). The MM-OEO uses electrical injection locking of an RF signal to the MM-OEO cavity modes in order to provide either loss or gain for specific RF frequencies. The drawback of the MM-OEO, however, is the mode spacing depends on the length of the cavity. Additionally, the ratio between loss and gain is limited to approximately 25 dB and the frequencies which receive gain cannot be tuned. Accordingly, there is a need in the art for better discrimination low power RF signals.